Deprecate egui_glium - looking for new maintainer (#2668)

* Deprecate egui_glium - looking for new maintainer

egui_glium was the first backend of egui, and it served us well for
a long time, but we have long since moved on to glow and wgpu.

Not egui_glium is holding back an update to latest winit.

Since development on glium has long since been discontinued I will
therefore deprecate egui_glium with this PR.

The code is still there in the repository for a while longer,
but is no longer compiled.

If there is any interest in maintaining egui_glium, then fork it and
make a PR to remove the last egui_glium from this repository.
I will give you publish rights on crates.io.

* update glutin 0.30.2 -> 0.30.3

* cargo update -p backtrace

    Updating crates.io index
    Updating addr2line v0.17.0 -> v0.19.0
    Updating backtrace v0.3.66 -> v0.3.67
    Updating gimli v0.26.2 -> v0.27.1
    Removing miniz_oxide v0.5.4
    Updating object v0.29.0 -> v0.30.3

* cargo deny: allow duplicates of windows-sys, wayland-sys, and nix

* cargo-deny whitelist tiny-skia

Cargo.toml

@@ -5,7 +5,6 @@ members = [
     "crates/egui_demo_app",
     "crates/egui_demo_lib",
     "crates/egui_extras",
-    "crates/egui_glium",
     "crates/egui_glow",
     "crates/egui-wgpu",
     "crates/egui-winit",